Measuring Sodium Transport in Cells with Nuclear Magnetic Resonance.

Area of Science:

• Biophysics
• Cell Biology
• Medical Imaging

Background:

• Sodium ions (Na+) are crucial for physiological functions, but their transport dysregulation is linked to diseases.
• Existing methods for measuring cellular Na+ activity are often invasive or lack dynamic range.
• Accurate assessment of Na+ transport is vital for understanding cellular health and disease.

Purpose of the Study:

• To develop a noninvasive method for quantifying sodium ion (Na+) transport rates in living cells.
• To investigate Na+ dynamics on a subsecond timescale using nuclear magnetic resonance (NMR).
• To establish quantitative markers for transmembrane ion dynamics and cellular metabolic activity.

Main Methods:

• Utilized ²³Na nuclear magnetic resonance (NMR) combined with relaxation exchange spectroscopy (REXSY) and a multisite exchange model.
• Employed endogenous NMR relaxation differences to distinguish intracellular and extracellular Na+ pools without exogenous reagents.
• Applied the technique to human cell lines to assess Na+ transport under various physiological conditions.

Main Results:

• Successfully quantified Na+ transport rates and intracellular Na+ fractions in living cells.
• Demonstrated the ability to differentiate between physiological states, including pharmacologically modulated ion channel activity.
• Observed a clear correlation between measured Na+ transport rates and cellular metabolic activity.

Conclusions:

• The developed ²³Na NMR REXSY method offers a noninvasive and direct quantification of cellular Na+ transport dynamics.
• This technique provides valuable quantitative markers for monitoring transmembrane ion flux and cellular metabolic status in vitro.
• The findings open new avenues for studying diseases associated with Na+ dysregulation.